1. Field of the Invention
The present invention is generally related to machining ceramic substrates, and in particular, polishing substrates.
2. Description of the Related Art
Machining, and in particular, polishing of substrates is widely used for formation of various devices, including microelectronic devices. For example, during wafer processing to form integrated circuit devices, wafers are subjected to chemical-mechanical polishing (CMP) to remove layers and planarize the wafer. In the area of magneto-resistive (MR) head manufacture, aluminum alloy substrates are polished to form jigs, and air-bearing surfaces of read/write heads for hard disk drives (HDD's) are polished and planarized.
In the context of machining, abrasive slurries are commonly used in lapping operations as well as polishing operations. Lapping generally denotes processes utilizing fairly large abrasive particles (e.g., 2-10 microns), and associated high material removal rates. Polishing, on the other hand, generally takes advantage of smaller abrasive particles, yields fairly low material removal rates, and superior surface finishes. Typically, one of the goals of a polishing operation is to provide a planar surface having relatively low surface roughness, free of defects such as scratches, “orange peel,” and “pull-out” of material along the exposed surface of the substrate. In addition, with respect to substrates having multiple phases of materials that are being polished (e.g., a hard ceramic portion and a soft conductive layer, such as in the case of HDD recording heads), it is also important to engineer a polishing operation which has a consistent material removal rate across different materials, so as to prevent selective polishing of soft materials of the substrate.
In an effort to increase polishing rates, reduce material removal selectivity, and reduce defects, polishing technology has evolved to combine mechanical removal (i.e., abrasion) of substrate material, along with a chemical reactive process. Such processes have been described in the industry as chemical-mechanical polishing, CMP, as noted above. The development of CMP processes and slurries containing such chemical and mechanical components have been intensely studied in certain areas such as semiconductor processing. However, a need continues to exist in the art for improved machining operations and slurries for carrying out such operations, and in particular, slurries and operations intended to polish aluminum-containing ceramics, such as alumina, alumina composites, non-oxide aluminum containing ceramics and the like.